Why can't detectors see gold chains very well?

[blacktoe]

I have tested 3 different detectors on gold chains. I have tried doubling, straight out, and a pile. Only 1 detector will get a hit and then not very good. With rings all 3 hit good tho at different depths depending on the detector. It looks like the chance of finding a chain is pretty slim. The chains I have are both the rope kind. I don't know if the herringbone or link kind will do different.


blacktoe

 

[Willee - Texas]

Here is how I have had it explained to me in the past.

The RF energy from the detector coil sets up an eddy current in the metal it detects.
This eddy current is what the detector is actually detecting.
Gold chains are made up of many small links.
The small links produce small eddy currents and it is as if the detector is trying to detect just one small link at a time.
So while you might have a large mass of gold, it is like one single link to the detector.
Usually, the clasp is the largest part of the chain and that is what you detect.

I have found many things that obviously were on a chain and have looked and looked for the chain with no luck and have often wondered how many small gold chains there are in the beach sand that are undetectable by most detectors.

Here is a test for you to do ... air test you detector with one dime.
Now glue three dimes on a stick and air test them.
Would you expect the three dimes to air test further away from the coil?
Did they?

A gold detector, or a detector set to the prospecting mode, will detect a small gold chain much better.

Willee

 

[silversmith]

Because detectors love round CLOSED turns like a ring or coin. A chain is a bunch of little pieces of metal hooked together but not necessarily making electrical contact. So even if you turn one in a closed circle, it probably won't be detected. Lets put it this way, if you take a piece of copper wire and lay it down on the ground, it will be hard to detect. And if you bend into a circle , making sure the ends don't quite touch (like a chain) you will still have a hard time finding it. If, however you twist the ends of the wire together, your detector will find it easily. Has to do with induced eddy currents. Does that help a little? I think only engineers understand, and I believe even they are a little confused

 

[Elton]

n/t

 

[slingshot]

If you want an eye opener, take the lowly BFO unit and test them with the gold chains. lt's really scary that these units will usually detect one to at least 3" with the finer ones still giving a weak signal. Even though mineralized ground inhibits their depth, I found 2 gold chains together at a beach-looked like a clump of moss-they were very fine and the moss had gathered on them because no one could detect them. The astounding thing is that the lowly BFO will ignore hairpins, paperclips, staples, and tiny nails while doing this. Ask me why I still have mine.

 

[Rebel1]

Ok i'm new at all this. What is a BHO?

 

[silversmith]

Stands for Beat Frequency Oscillator. Operates under the theory a metal object will change the frequency of an oscillator that the search coil in the tank circuit is in proximity too. Beating a second oscillator on close to the same frequency will produce an audio note that you can hear. These things can be very sensitive because your ear can detect minute changes in frequency much better than it can detect changes in amplitude (volume) like a TR. Wasn't developed fully 'cause it's much harder to make a discriminating B.F.O. detector. Does this help?

 

[blacktoe]

Thanks for the answers guys.

Special thanks to Willee and silversmith for putting it in terms I understand.

blacktoe

 

[oldandtired]

n/t

 

[slingshot]

Ok i'm new at all this. What is a BHO?

I'm just showing how old I am! The BFO went out with us old codgers because miineralization would cut down on their depth and the discrimination,even at it's best left a lot to be desired. However, it NATURALLY ignores these hairpins, nails,etc. and would be still great for totlots and whereever shallow beep-dig scenarios with the possibility of tiny gold chains, rings, earrings,etc exist. It has an annoying constant motorboat sound and the detector package is bulky and uncomfortable. I plan to build one with one IC chip, the CMOS 4030 or 3040, can't recall right now (sometimer's setting in) and place it in a walking cane configuration for tot lots and call it the TOTLOTER.

 

[Dan-Pa.]

For you freshwater beach or shallow water hunters get yourself an older hipmount Tesoro where you can tuck the box in your waders for shallow water hunting. Turn down the Disc. to Zero and a fishook or bobbi pin will chatter but a small gold chain will hit. Don't know why it only works for older Tesoro's but certainly one of the best and yes certainly works well for larger gold jewelry also..

 

[UK Brian]

The BFO was the general purpose machine of its time especially after Garrett had improved the discrimination and introduced zero drift circuitry. By the late 70's they still performed well in most treasure hunting tasks but the advertising was change to something along the lines that if you appreciated the benefits of B.F.O. operation BUT were prepared to accept that it would not provide the depth of the VLF/TR then buy with confidence.

Problem with many machines such as the Sovereign as far as fine chains and very thin gold rings is that people accept the low tone they give as being what we call hair grips (same as your bobby pins ?) and don't bother to dig whereas the target should be checked in all metal which will indicate if its worth digging or not.

There's still many of the older machines that can earn their keep. Hopefully someone will have a look at the off-resonance design's again. True discrimination that shows up many a modern detector. Again the problem was a lack of depth but further development may well have found a way round that.

 

[silversmith]

Hey slingshot, keep us posted on the cmos bfo progress. I built several detectors years ago using discreet technology. They were very stable. I made the search loop the variable or tuned osc and xtal controlled the beat osc. I found for more more sens I could use a xtal at twice the loop freq and catch the second harmonic of the search loop. Good luck to you.......!

 

[slingshot]

Hey slingshot, keep us posted on the cmos bfo progress. I built several detectors years ago using discreet technology. They were very stable. I made the search loop the variable or tuned osc and xtal controlled the beat osc. I found for more more sens I could use a xtal at twice the loop freq and catch the second harmonic of the search loop. Good luck to you.......!

Thanks, Silversmith. I had looked at a crystal filter design by Charles Rakes and was interested in that but the tuning capacitors aren't that available anymore around here. Besides, would have been pretty hard to put inside a small area. Thanks for the tech info-tho' I'm not that well versed.

 

[Uncle Willy]

Because the detector only sees one link at a time - not the whole chain.

Bill

 

[Uncle Willy]

They also drifted a lot and had to be retuned.

Bill

 

[UK Brian]

n/t

 

[UK Brian]

I find a reasonable amount of gold chains but rarely with my Sovereign or Whites Beach Hunter ID as a good pulse machine copes so much better.
Inland the Minelab Eureka at 20 or 60 kHz will do the business. For the beach with a pulse the best results are if a smaller coil is fitted or you could get a machine like the Tesoro pulse that has a spiral coil to increase sensitivity to items such as fine chains.
If your not doing to well with chains you also will not be finding the hundreds of broken rings that remain on the beaches. The gold is just as good as far as the scrap man is concerned.

 

[silversmith]

"They also drifted a lot and had to be retuned." Oh, not necessarily. Cheapies did. But the GOOD stuff, notably Garrett's would "putt-putt" for seemingly hours and never change note. Again, A.H. came out with a TR that discriminated so well, everything was Kapoot! My opinion.

 

[slingshot]

"They also drifted a lot and had to be retuned." Oh, not necessarily. Cheapies did. But the GOOD stuff, notably Garrett's would "putt-putt" for seemingly hours and never change note. Again, A.H. came out with a TR that discriminated so well, everything was Kapoot! My opinion.

Yeah. The AH was an off-resonance discriminator that was awesome. Can't believe I sold mine-but I was so hung up on discriminating out tabs I didn't realize it's other uses. My Garrett Hunter is steady with only an occasional retuning if I bump the coil or controls-it will change tuning if the coil is bumped and gets closer or farther away from the stem.